Enzymes decomposing proteins and peptides are nowadays produced by separating them from the animal digestive tract, from animals' digestive glands, from other animal tissues, from plant tissues, and in recent years also by cultivating bacteria, yeasts, moulds and actinomycetes producing such enzymes.
However, the majority of the protein and peptide decomposing enzymes known in prior art have been endopeptidases, that is they decompose protein molecules by breaking peptide bonds within the molecules. Exopeptidases, that is enzymes isolable and producible on a technical scale which hydrolyse the peptide bonds close to the ends of the molecules, have been few. It is moreover noted that in most cases the entzymes had a highly specific, that is they break exactly specified bonds or correspondingly produce certain specific compounds, whereby the available selection of enzymes has been insufficient to meet practical needs in technology, food processing, medicine and research. Furthermore, the enzymes hydrolysing activity of known proteins has been unsatisfactory: for instance, the protease of Streptomyces griseus, which is considered the most efficiently protein-hydrolysing microbial enzyme, is only able to set free about 55% of the amino acid residues in casein into amino acids.